PFAS is short for 'Per- and poly- FluoroAlkyl Substances'. The Teflon that's used on your pans, which are 'poly-' materials, comes in extra long chains (hundreds of thousands of molecules). Most of its chemical bonds are hidden behind the extremely reactive Fluoride atoms (so if Fluoride is bonded onto that position, it's hard to take it off) and are extremely inert, so they don't interfere with typical biological reactions, thus are perfectly safe.
C8 is known as PFOA (perfluorooctanoic acid). Per for its chained molecule shape (no carbon side chains), 'fluoro' for the F part, 'octanoic' for the 8 carbon atoms, and 'acid' for its chemical property. Unlike Teflon:
- C8 has a really small molecular mass, making it easier to flow around your body participating in all kinds of biological operations;
- It is an acid (having the carboxylic '-COOH' group) and can pretend to be all kinds of acids and actively take part in reactions. Once they start to get inside, the consequences can be unpredictable and devastating.
- All other atoms on C8 except for the last -COOH group are covered by fluoride atoms. This means that C8 is not biodegradable (no enzyme can break apart the C-F covalent bond since it's bond energy is really too high), and when it gets into the environment, it stays that way.